package me.yuzho.study.concurrency;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

class CircularSet {
    private int [] array;
    private int len;
    
    private int index = 0;
    
    public CircularSet(int size) {
       
        array = new int[size];
        
        len = size;
        
        // Initialize to a value not produced by the SerialNumberChecker
        for(int i=0; i<size; i++) {
            array[i] = -1;
        }
    }
    
    public synchronized void add(int i) {
        array[index] = i;
        index = ++index % len;
    }
    
    public synchronized boolean contains(int val) {
        for(int i=0; i<len; i++) {
            if(array[i] == val) return true;
        }
        return false;
    }
}


public class SerialNumberChecker {
    
    private static final int SIZE = 10;
    private static CircularSet serials = new CircularSet(1000);
    private static ExecutorService exec = Executors.newCachedThreadPool();
    
    static class SerialCheck implements Runnable {
        public void run() {
            while (true) {
                int serial = SerialNumberGenerator.nextSerialNumber();
                if(serials.contains(serial)) {
                    System.out.println("Duplicate: " + serial);
                    System.exit(0);
                }
                
                serials.add(serial);
            }
        }
    }
    
    
    public static void main(String[] args) throws NumberFormatException, InterruptedException {
        
        for(int i=0; i<SIZE; i++) {
            exec.execute(new SerialCheck());
        }
        
        if(args.length > 0) {
            TimeUnit.SECONDS.sleep(new Integer(args[0]));
            System.out.println("No duplicates found ");
            System.exit(0);
        }

    }

}
